1. Technical Field
The present invention relates to printed circuit boards, particularly to a printed circuit board substrate and a method for manufacturing a batch of printed circuit boards.
2. Description of Related Art
Rigid-flexible printed circuit boards (R-F PCBs) are widely used in electronic devices. Rigid-flexible printed circuit board has a rigid region and a flexible region. The rigid region is configured for assembling electronic components and maintaining electrical connections among the electronic components. The flexible region is connected to the rigid region and can be bent relative to the rigid region. Thus, the rigid-flexible printed circuit board can be assembled with a number of electronic components, and occupies small space by bending the flexible region.
A typical method for manufacturing a batch of rigid-flexible printed circuit boards is shown in FIGS. 13-17. As shown in FIG. 13 and FIG. 14, a rigid-flexible printed circuit board substrate 30 includes a rigid substrate 31 and three flexible substrates 32 laminated thereon. The rigid substrate 31 includes a resin layer 311 and a copper layer 312 configured to form predetermined electrically conductive patterns on the resin layer 311. The rigid-flexible printed circuit board substrate 30 defines three processing regions 310, each of corresponds to a flexible substrate 32. Each of the flexible substrates 32 includes an insulation layer 321 and a plurality of electrical traces 322 formed thereon. As shown in FIG. 15 and FIG. 16, a photolithographic process is performed to make a predetermined electrically conductive patterns from the copper layer 312 on the resin layer 311.
The photolithographic process is described in detail as following. Firstly, referring to FIG. 15, a photoresist layer 40 is applied on the copper layer 312 and covers the three processing regions 310. Secondly, the photoresist layer 40 is exposed by UV-light passing through a photo mask 50. The photo mask 50 has three exposing sections 51, each of which has pattern-like openings 510 defined therein. Thirdly, referring to FIG. 16, the photoresist layer 40 is developed, the copper layer 312 is etched to form predetermined electrically conductive patterns 312a, and the residual photoresist layer 40 is removed. After the photolithographic process, plated through holes (not shown) are formed in the rigid-flexible printed circuit board substrate 30 to interconnect the electrically conductive patterns 312a and the electrical traces 322 of the flexible substrates 32. Then the rigid-flexible printed circuit board substrate 30 is cut along imaginary boundary lines between the manufacturing regions 310, and three rigid-flexible printed circuit boards 60 are obtained as shown in FIG. 17.
In the photolithographic process, the photo mask 50 should be precisely aligned with the rigid substrate 31 when the photoresist layer 40 is exposed because the electrical traces 322 of the flexible circuit board 32 should be corresponding to the electrically conductive patterns 312a of the rigid substrate 31. If the photo mask 50 deviates from desired position, the electrical conductive patterns 312a would not align with the electrical traces 322 and could not be electrically connected to the electrical traces 322 by plated through holes, thereby a quality of the batch of rigid-flexible printed circuit boards 60 is affected.
What is needed, therefore, is a method for manufacturing a batch of printed circuit boards which can overcome the above-described problems.